This invention relates to making integrated circuits and more particularly to methods for making hafnium based layers such as hafnium oxide.
A variety of different materials have been studied as candidates for future gate dielectrics for advanced integrated circuits. The need for these gate dielectrics having a high dielectric constant (high K) is that the commonly used material silicon oxide needs to be made thinner and thinner in order to achieve the coupling between the gate and the channel that is needed as advances continue. The thinning of the silicon oxide eventually leads to unacceptable gate leakage. Some of the most common high K materials targeted to replace silicon oxide are metal oxides. Some of the more commonly studied metal oxides are zirconium oxide, titanium oxide, and tantalum oxide. These all provide the high K that is needed, but they also introduce additional problems. Commonly, various chemicals are used in the formation of these metal oxides. In the formation of the metal oxide, some of these chemicals leave unwanted byproducts or impurities in the metal oxide itself. This comes about by the nature of using chemical precursors to form the metal oxide. The typical precursor is a metal chloride or metal organic. Often, some chlorine or carbon will remain in the metal oxide. For an insulator, this is particularly undesirable because impurities tend to reduce the insulating characteristics of an insulator.
With respect to zirconium oxide, one of the disadvantages is that the zirconium oxide may react with the gate that overlies the zirconium oxide if that gate is silicon. Silicon is the typical choice for gates. At the anneal temperatures that are required for activating the source/drain are sufficient to cause a reaction between the zirconium oxide and the silicon. Titanium oxide and tantalum oxide actually have the same problem but to an even greater degree. Of course some of the alternatives are to use a metal gate instead of a silicon gate, but this also requires development of the proper choice of the proper gate and the metal gate itself may introduce different problems.
Thus it is shown there is a need for a method of making a high quality high K dielectric material that avoids the problems of zirconium, titanium, and tantalum oxide films.